import numpy as np
import pandas as pd

a = pd.Series([1,2,3,4], index=['a','b','c','d'])
b = pd.Series([1,2,3,4], index=['c','b','a','d'])
c = pd.Series([1,2,3,4,9], index=['b','e','a','c','d'])

print(a + b)
print(a + c)
print(a.add(c, fill_value=0))
print(a.sub(c, fill_value=0))
print(a.div(c, fill_value=0))
print(a.mul(c, fill_value=0))
